In general, switches are utilized to switch devices from an open/off position to a closed/on position in order to control the operation of particular devices and/or systems. Pressure switches are widely utilized for controlling electrically operated devices by switching an electrical contact between open and closed circuit positions based on a preset fluid pressure threshold. Pressure switches provide a reliable indication of a fault indicative pressure while simultaneously obviating switch actuation caused by excess pressures. Such pressure-sensitive switches can be utilized in a wide variety of applications such as, for example, fuel, hydraulic, potable water, and engine oil pressure systems.
An absolute pressure switch essentially needs to maintain vacuum inside the pressure switch for precise measurement of a media such as a liquid or gas flowing through a system. Such absolute pressure switches can be utilized in aerospace applications in order to effectively regulate pressure relative to the aircraft system requirements. The majority of prior art absolute pressure switches are typically configured with an elastomeric diaphragm that is impinged upon by the media under pressure. The diaphragm may actuate the switch contacts of the pressure switch upon reaching a predetermined pressure. Such pressure switches, however, tend to operate only at relatively low pressure levels and are not sufficiently miniaturized, since they frequently occupy more space.
The elastomeric diaphragm may be affected by surrounding dust, which tends to damage the diaphragm, particularly when it is not properly sealed. Additionally, in harsh conditions (e.g., extreme temperatures) such diaphragms may stiffen at cold conditions, thereby leading to a change in a predetermined set point. Furthermore, these types of elastomeric diaphragms tend to breathe over a period of time, which induces drift in the set point.
Note that other types of conventional pressure switches may include the use of a push member, two contact points, a spring member and an enclosure, which receives all the parts therein. Such a pressure switch may improve the switching operation, but increases its overall size and manufacturing costs.
Based on the foregoing, it is believed that a need exists for a low cost, absolute pressure switch apparatus for providing hermetic sealing and maintaining switch set point accuracy at high and low temperature ranges. It is also believed that a need exists for an improved switch actuation mechanism, as described in greater detail herein.